1. Field of the Invention
The present invention relates to an apparatus for adjusting the height of a swivel chair, and more particularly to a gas cylinder type height-adjusting apparatus of a swivel chair which has a simple structure and thereby can be manufactured at a low cost.
2. Description of Prior Art
In general, a swivel chair has a part named as a spindle which performs functions of not only supporting the weight of a person seated thereon but also adjusting the height of the chair according to the physique of the person.
The spindle is an important part of a swivel chair in adjusting the height of the chair and can be classified as two types according to the height-adjusting manner, including a screw-adjusting type using a screw spindle and a gas cylinder type in which usually a nitrogen gas functions as a working fluid.
FIG. 1 is a sectional view of a conventional height-adjusting apparatus of a swivel chair having a gas cylinder type spindle for showing the construction thereof. In FIG. 1, reference numeral 10 designates a spindle having a shape of a cylinder. The spindle 10 is inserted in an outer tube 20 having a larger diameter, and a piston rod 30 is inserted into the spindle 10 through the bottom of the spindle 10.
A top stopper 16 is fixed to the top of the spindle 10, and an actuating protuberance 14 is slidably fitted in the top stopper 16. The actuating protuberance 14 is connected to a height-adjusting lever (not shown) for adjusting the height of the swivel chair. A pushing rod 18 integrally formed under the actuating protuberance 14 is in contact with an actuating pin 19. The actuating pin 19 is slidably fitted in an actuating pin socket 40 so as to slide up and down therein. The actuating pin socket 40, whose more detailed construction will be given later, is fixed in the spindle 10 with providing gas-tight therein.
The outer tube 20 of a cylindrical shape has a spindle support 50 fixed to a lower part of the outer tube 20. The piston rod 30 is fixed to the spindle support 50. The spindle 10 has a spindle neck 12 at an upper part thereof which is tapered so as to be inserted in a seat (not shown) of the chair.
The spindle 10 surrounds a cylinder 44 which has a smaller diameter than the spindle 10. The spindle 10 has a buffer disposed in the spindle 10 for providing a comfortable feeling for the person seated thereon. A thrust bearing 60 is arranged on the spindle support 50 so as to ensure a smooth swivel of the chair with bearing the weight from above. The reference numeral 62 designates a cushion such as a rubber which comes into contact with the bottom of the spindle 10. The cushion 62 buffers the impact on the bottom of the spindle 10 when the spindle 10 is lowered down to its lowermost position.
The bottom of the piston rod 30 is detachably installed on the spindle support 50 by means of a clip 70. In FIG. 1, the reference numeral 52 designates a spindle holding member which is disposed between the spindle 10 and the outer tube 20 so as to hold the spindle 10 in such a manner that the spindle 10 can slide therethrough into and out of the outer tube 20.
FIG. 2 is an enlarged sectional view of the actuating pin socket 40 disposed in the spindle 10 of FIG. 1. As shown, the actuating pin socket 40, shaped roughly like a cylinder, has an actuating pin hole 41 formed through the center of the actuating pin socket 40 in which the actuating pin 19 is fitted. The actuating pin socket 40 also has a plurality of socket O-ring grooves 43 formed around the outer circumferential surface of the actuating pin socket 40 in each of which a socket O-ring 45 is fitted.
The inner center portion of the actuating pin socket 40 forms a central space 46 for passing gas therethrough in which at least two socket O-rings 45 and an inner holder 47 are arranged. The socket O-rings 45 maintain gas-tight in the central space 46, and the inner holder 47 holds the socket O-ring 45 of the inner side and helps smooth sliding of the actuating pin 19. The actuating pin socket 40 has an orifice 42 formed at one side of the actuating pin socket 40. The orifice 42 is connected to an outer space of the cylinder 44. The inner holder 47 has a connecting pore 47a formed at one side of the inner holder 47 and connected to the orifice 42.
Referring to FIG. 2, the actuating pin 19 has a small-diameter portion 19a formed at a middle portion of the actuating pin 19. The small-diameter portion 19a has a diameter smaller than that of the remaining portion of the actuating pin 19. When the actuating pin 19 is lowered down, the small-diameter portion 19a makes a small gap between the actuating pin 19 and the actuating pin socket 40, so that gas filled in a first chamber A can flow into the central space 46 of the actuating pin socket 40 and then into a second chamber B through the orifice 42. In FIG. 2, reference numeral 13 designates a holding washer provided in the actuating pin socket 40 to hold the socket O-rings 45 in the actuating pin socket 40. Nitrogen gas and oil are filled in the first chamber A, as working gas and fluid.
FIG. 3 is an enlarged sectional view for showing the construction of a piston 80 installed at the top of the piston rod 30 in detail, and FIG. 4 is an enlarged sectional view for showing the operation of the piston 80.
The piston rod 30 has a piston rod head 87 which prevents the piston rod 30 from being separated from the piston 80. The piston 80 has a plurality of inner and outer O-ring grooves in each of which a piston O-ring 82 is fitted to make gas-tight. The piston 80 has various parts which enable the piston 80 to smoothly and closely slide in the cylinder 44 and prevent the piston 80 from coming out of the spindle 10. The bottom of the spindle 10 is bent inward so as to prevent the piston 80 from escaping.
The spindle 10 houses a flange 83 disposed in the bottom thereof and a sealing member 84 disposed on the flange 83 for maintaining gas-tight in the cylinder 44. Between the piston 80 and the sealing member 84, an annulus 85 and a cylinder holder 86 are arranged in order from above. The annulus 85 surrounds a spring ring 88 for fixing the piston 80 to the piston rod 30, and the cylinder holder 86 supports the bottom of the cylinder 44.
Referring to FIG. 4, the cylinder holder 86 has a gas-passing hole 86a formed through an outer portion of the cylinder holder 86. The gas-passing hole 86a provides a path from the second chamber B to the third chamber C. Therefore, the gas-passing hole 86a enables the gas to flow from the first chamber A through the second chamber B into the third chamber C. Arrows in FIG. 4 shows the gas flow from the second chamber B to the third chamber C.
FIGS. 5A and 5B are respectively an exploded and an assembled elevations of the actuating pin 19 employed in the conventional gas cylinder type height-adjusting apparatus shown in FIG.1. The actuating pin 19 has a small-diameter portion 19a and two large-diameter portions 19b. The small-diameter portion 19a is integrally connected to each of the large-diameter portions 19b through a sloping portion 19c. The lower large-diameter portion 19b has an actuating pin neck 19d protruding downward from the bottom of the large-diameter portion 19b.
Referring to FIG. 5B, the actuating pin neck 19d is inserted in a fixing washer 17 and then a holding head 19e is assembled at the lower end of the actuating pin neck 19d, so as to fix the fixing washer 17 thereto. The fixing washer 17 comes apart from the holding washer 13 when an external force as shown by an arrow in FIG. 2 is applied, while the fixing washer 17 comes into contact with the holding washer 13 when the pressure of the gas filled in the first chamber A is applied to the fixing washer 17. Reference numeral 17a designates a fixing washer hole formed at the center of the fixing washer 17 so as to receive the actuating pin neck 19d.
FIG. 6 is an enlarged sectional view of the actuating pin 19 and the actuating pin socket 40 for showing the operation of the actuating pin 19 in the actuating pin socket 40. When the actuating protuberance 14 shown in FIG. 1 is pressed by means of the height-adjusting lever (not shown), the pushing rod 18 formed integrally with the actuating protuberance 14 pushes down the actuating pin 19, which state is shown in FIG. 6.
When the actuating pin 19 is pushed down, the small-diameter portion 19a of the actuating pin 19 is lowered down so as to make the first chamber A and the central space 46 intercommunicate with each other. In this case, the gas in the first chamber A flows through the central space 46, the connecting pore 47a and the orifice 42 into the second chamber B. Moreover, the gas flown into the second chamber B from the first chamber A continues to flow to the third chamber C through the gas-passing hole 86a shown in detail in FIG. 4.
FIG. 7 is a sectional view of the conventional height-adjusting apparatus of FIG. 1 for showing the descending operation of the gas cylinder type spindle 10. As the gas in the first chamber A decreases while the gas in the third chamber C increases, the piston 80 is pushed up due to the change of the pressure difference between the two chambers, as shown in FIG. 7. In other words, the pressure of the gas in the third chamber C, which is larger than that in the first chamber A, pushes the piston 80 up and the spindle 10 down, to thereby lower the spindle 10 down because the piston 80 is fixed to the spindle support 50 of the outer tube 20 by means of the piston rod 30.
The above described conventional height-adjusting apparatus of the gas cylinder type has following problems.
First, the actuating pin socket 40 is made of metal, usually of aluminum because it can be easily treated. However, aluminum is very expensive and apt to be damaged in the course of being treated. Therefore, there is a high possibility that the manufactured goods of the actuating pin socket 40 has defects such as scratches on its surface, despite the fact that the actuating pin socket 40 must have a surface of a high accuracy for ensuring the gas-tight characteristic.
Second, the complicated construction of the actuating pin socket 40 increases the manufacturing cost and disturbs its mass production. Third, the socket O-ring 45 and the inner holder 47 assembled with the actuating pin socket 40 increase manufacturing steps and labor power. Fourth, even when all parts of the actuating pin socket 40 excepting the socket O-rings 45 are manufactured by injection molding, there remains a molding line between the upper mold and the lower mold on the actuating pin socket 40, which requires a further finishing step in manufacturing the actuating pin socket 40 and lowers the surface accuracy of the manufactured actuating pin socket 40.
Fifth, the conventional actuating pin 19 must have a high accuracy of its size for ensuring the gas tight characteristic in spite of being made from relatively hard material. However, the actuating pin neck 19d for fixing the fixing washer 17 makes the construction of the actuating pin 19 more complicated to thereby require relatively hard labor in its manufacturing, disturb its mass production, and increase its manufacturing cost. Further, the assembling of the holding head 19e with the actuating pin neck 19d can have an impact on the remaining portions of the actuating pin 19, so as to make distortion in the actuating pin 19, which is not preferable for a part requiring a high accuracy.
Sixth, the piston 80 requires a further manufacturing step of assembling the piston O-ring 82 on the inner and outer surfaces of the piston 80, which increases the required labor and expense. Seventh, it is very difficult to assemble the piston rod 30 with the outer tube 20, and the piston rod 30 is apt to be separated from the outer tube 20 even after the assembling.
FIGS. 8 to 10 show another conventional height-adjusting apparatus of a swivel chair having a screw type spindle. FIG. 8 is an exploded perspective view of the conventional screw type height-adjusting apparatus of a swivel chair, and FIGS. 9 and 10 are perspective views of two types of conventional shaft bearing members employed in the conventional screw type height-adjusting apparatus of FIG. 8.
In FIG. 8, reference numerals 100 and 200 respectively designate an outer tube and a spindle installed in the outer tube. The outer tube 100 is cylindrical, and the spindle 200 has an inner tube 240 of a cylindrical shape and a spindle neck 220 connected integrally to the inner tube 240. The inner tube 240 has a plurality of dents 242 for holding a support ring 320. The spindle neck 220 is tapered so as to be inserted in a seat (not shown) of the chair. The spindle 200 houses an elastic buffer 300 for ensuring comfort of the seated person, a shaft bearing member 500 for ensuring a smooth swivel of the spindle, a rubber ring 600 for maintaining the height of the chair, and a screw nut 700 and a clutch 800 for adjusting the height of the chair.
Reference numerals 120, 320, and 502 respectively designate a spindle guide disposed between the outer tube 100 and the spindle 200 to support them, a support ring disposed between the stopping dents 242 and the elastic buffer 300, and balls fitted in the shaft bearing member 500. Reference numeral 590 designates bearing supports disposed respectively on and beneath the shaft bearing member 500 to protect it.
The spindle 200 also houses a screw shaft 900 passing through the elastic buffer 300, the shaft bearing member 500, the rubber ring 600, the screw nut 700, and the clutch 800. A screw shaft disc 910 is installed at the bottom of the screw shaft 900. The screw shaft disc 910 has a circular screw shaft hole 912 for preventing the screw shaft 900 from idly rotating. A nut support 920 limits descending of the screw nut 700.
The clutch 800 is fixed to the bottom of the spindle 200. The screw nut 700 has a sloping groove 720 and a plurality of teeth grooves 780 respectively formed at the upper and the lower surfaces thereof. The clutch 800 has a plurality of teeth 820 formed on the upper surface thereof. The sloping groove 720 receives the rubber ring 600, and the teeth 820 are engaged with the teeth grooves 780.
Referring to FIG. 9, the shaft bearing member 500 contains a plurality of the balls 502. Therefore, when a weight is loaded, the bearing supports 590 disposed on and beneath the shaft bearing member 500 are in contact with the balls 502, so as to reduce the sliding resistance, thereby ensuring a smooth swivel of the chair. In FIG. 9, reference numeral 504 designates a hole for passing the screw shaft 900 therethrough.
However, the above shaft bearing member 500 has at least four balls 502 for ensuring the smooth swivel of the spindle 200. This structure causes a problem; that is, the metal balls 502 inserted in the shaft bearing member 500 of hard synthetic resin can cause a structural problem. Further, this metal-ball-containing shaft bearing member 500 has many problems such as complicated manufacturing process, problematic durability, and expensive manufacturing cost.
Referring to FIG. 10, the shaft bearing member 500 has an outer cylindrical wall 510 and an inner cylindrical wall 520 integrally connected to each other through a plurality of bridges 530. The bridges 530 have a smaller vertical width than the outer cylindrical wall 510 and the inner cylindrical wall 520. The bridges 530 provide a grease-filling gap 540 between the outer cylindrical wall 510 and the inner cylindrical wall 520 and each of the bridges 530 has a grease-flowing groove 550, so that grease can be filled and freely flow in the grease-filling gap 540 through the grease-flowing grooves 550. The shaft bearing member 500 can be made from material selected between hard synthetic resin and metal. Reference numeral 560 designates a hole formed at the center thereof so as to pass the screw shaft 900 therethrough.
In this type of the shaft bearing member 500 shown in FIG. 10, grease filled in the grease-filling gap 540 protects frictional parts to thereby enhance the durability of the shaft bearing member 500. However, the shaft bearing member 500 has a very complicated structure, because the outer cylindrical wall 510, the bridges 530, and the inner cylindrical wall 520 are integrally connected one another and the shaft bearing member 500 has the grease-filling gap 540 and the grease-flowing groove 550. Therefore, it is difficult to manufacture the metal mold of the shaft bearing member 500, and the manufacturing cost of the shaft bearing member 500 is increased.